Seeing the Forest for the Flying Squirrels

By Matt Miller

Alaskan researchers track flying squirrels to determine how much forest they need to thirve. Colin Shanley/TNC
Alaskan researchers track flying squirrels to determine how much forest they need to thirve. Colin Shanley/TNC

Flying squirrels glide through the trees with the greatest of ease — but only if they have a big enough patch of forest.

These little squirrels – with flappy skin between their hands and feet that enables them to glide effortlessly from tree to tree – can’t scamper around much on the ground. They need a forest, and preferably a diverse one.

But just how much forest does a flying squirrel need?

That was the focus of research recently published in the journal Ecological Indicators by Nature Conservancy ecologist Colin Shanley.

The information he learned about these small mammals’ habitat needs provides more data to help better manage Alaska’s Tongass National Forest. Forest managers are transitioning from historically large-scale clearcutting to local, small-scale, sustainable harvest of primarily young-growth stands in previously harvested areas.

Figuring out what wildlife need to survive is an important part of the forest management program.

Shanley conducted his research on Prince of Wales Island in Alaska, the third largest island in the United States. Once covered in old-growth forest, it’s also been subject to intense logging pressure.

“The forest here should be a working forest, but the way it was managed in the past didn’t allow for some important ecological functions that sustain fish and wildlife populations,” says Shanley.

The movements of critters – where they will and won’t go, where they feed, where they rest – can tell conservationists a lot about a forest. Ecologists know flying squirrels don’t need huge, unbroken wilderness, but they didn’t know how small a forest patch could be and still function as viable habitat. (Other research studied martens, which need mid-sized forests, and gray wolves, which roam over huge swaths of territory).

By determining habitat needs, forest management plans could be improved to allow ample harvest to support industry, while still maintaining healthy populations of creatures like flying squirrels.

The Flying Squirrel as Super Ball

First Shanley had to actually capture the squirrels. His team baited modified small mammal traps, baited with peanut butter, oatmeal and occasionally molasses, that snapped shut and captured the squirrels unharmed.

“Each squirrel has its own personality,” Shanley says. “The young ones tended to be really docile. I would find them sitting in the trap, and they’d just stare at you. I’d pick them up, and they would just sit there looking at you with their big eyes.”

Adult squirrels could prove a bit more exciting.

“In the breeding season, the males are totally energized,” he says. “He’ll be bouncing around the trap like a super ball. We had to put a pillow case over the trap and let the male blitz into it.”

Once captured, Shanley fitted the squirrels with radio transmitters that allowed researchers to track exactly where they traveled.

At first glance at the squirrel movements, the map might again look like a super ball was bouncing all through the forest. But unlike a super ball, the flying squirrel’s movements aren’t random at all. On closer analysis, the little squirrels focus on very specific habitats.

“The power of the analysis is looking at where they spend the bulk of their time,” says Shanley. “Sure, they’ll move through areas with just a few trees. But that’s basically just to move from one area to another. They really are spending most of their time in large, contiguous blocks of old-growth forest.”

In large part, the type of forest they prefer is simply tied to food: Flying squirrels eat fungus found on large trees. (In fact, some ecologists call them the “fertilizer of the forest” because they move beneficial fungi from tree to tree). These larger forests also help them hide from and evade a rogues’ gallery of predators: goshawks, owls, martens, weasels.

“When we started crunching the numbers, flying squirrels demonstrated a definite resource selection,” says Shanley. “They clearly are more successful at finding food in these big core patches.”

Shanley’s research determined that the minimum forest patch size needed to support a healthy flying squirrel population is 73 hectares (about 180 acres) – larger than many researchers believed they would need.

These data will help the U.S. Forest Service – the agency that manages a large block of the island on its Tongass National Forest – continue to improve the network of old growth reserves for wildlife conservation.

“A lot of what we’re focused on now is helping the Forest Service with the information it needs to transition from big, old growth timber sales to sustainable, small-scale management sales that support local economies,” says Shanley. “This study was one of many research efforts. Flying squirrels were an interesting species to study. They have a very interesting relationship with the forest and are very useful in studying the effects of forest management. The research was very specific, but it provides more evidence supporting the value of a diverse, old-growth forest.”

Matt Miller is a senior science writer for the Conservancy. He writes features and blogs about the conservation research being conducted by the Conservancy’s 550 scientists. Matt previously worked for nearly 11 years as director of communications for the Conservancy’s Idaho program. He has served on the national board of directors of the Outdoor Writers Association of America, and has published widely on conservation, nature and outdoor sports. He has held two Coda fellowships, assisting conservation programs in Colombia and Micronesia. An avid naturalist and outdoorsman, Matt has traveled the world in search of wildlife and stories.